172 FXUS63 KAPX 211337 AFDAPX Area Forecast Discussion National Weather Service Gaylord MI 937 AM EDT Sat Aug 21 2021 .UPDATE... Issued at 937 AM EDT Sat Aug 21 2021 Some cirrus over nw lower and eastern upper MI this morning, along with lingering smoke/haze aloft (smoke is thickest in ne lower MI). Otherwise a quiet start to the day, as early morning fog has eroded. 991mb surface low is well nw of Superior, with a cold front moving across western WI. Showers just ahead of this front were diminishing. The front will enter northern MI this evening. MlCape values increase to 500-600j/kg ahead of the front. With a weak shortwave kicking out across northern MI this afternoon, there perhaps will be just enough forcing for an isolated pre-frontal- band shower or two to develop. Better rain chances with the frontal band arrive in far western sections (western Chip/Mack Cos, Lake MI coast from the Dunes southward) early this evening. Neither shear nor instability is conductive to svr storms today/tonight. Mid 80s to around 90f for max temps today. && .NEAR TERM...(Today through Tonight) Issued at 405 AM EDT Sat Aug 21 2021 ...Rain and thunder chances return this evening... High Impact Weather Potential: Low Pattern Synopsis: A potent shortwave currently over the northern Great Plains will progress NE through Ontario today as ridging amplifies and pushes over Quebec. Favorable divergence aloft provided by the shortwave will deepen the associated cyclone over ND/MN down near 990mb as it works NE into Canada through the short term, pushing high pressure currently in place across the Great Lakes further east. An attendant cold front stretching far to the south of the cyclone center will slide across the Midwest today, eventually making it into the Great Lakes later this evening/tonight. Forecast/Details: Clear skies and calm winds have lead to patchy fog developing across parts of the area, but this is expected to mix out shortly after sunrise. Afterwards, sunny skies are expected through late morning before at least some cu develops this afternoon. Southerly low-level flow, albeit weak, will help advect a narrow corridor of more favorable moisture into northern Michigan immediately ahead of the advancing cold front this afternoon/evening. While this will help boost MLCAPE values near 1,000 J/kg, favorable upper-level forcing being displaced far to the NW and a general lack of shear will work to limit any severe thunderstorm potential. Regardless, showers and a few storms are expected across western portions of the CWA -- especially eastern upper and Tip of the Mitt -- associated with low- level convergence along the front where chances will diminish with eastward extent as any activity will move into an increasingly unsupportive environment. Showers/storms should diminish by the end of the period. Otherwise, another hot and humid day is in store for northern Michigan today. Afternoon highs will push 90 degrees for most across the area with dewpoints in the mid 60s. South/southwest winds around 10 mph this afternon will switch to northerly behind the front tonight. Low temps tonight will be close to 60 for most. && .SHORT TERM...(Sunday through Monday) Issued at 405 AM EDT Sat Aug 21 2021 High Impact Weather Potential: Minimal. Pattern Synopsis/Forecast: Large scale pattern shows a basic trough west/ridge east pattern across North America. Short wave trough lifting northeast through the mean trough position and across the Midwest...and another digging across the Pacific Northwest. Tropical cyclone "Henri" over the southwest Atlantic traveling parallel to the coast off the Carolinas. Another broad weakness in the pattern is over the eastern third of the CONUS which is helping to steer "Henri" northward. Narrow axis of deep moisture (precipitable water values 1.50-2.00+ inches lies ahead of the short wave trough axis from Minnesota south along the I-35 corridor. 995mb compact surface low lies along the southern Manitoba border...cold front trails south across western portions of Minnesota and Iowa/eastern Kansas. Height falls with trough lifting northeast through the Midwest will pass mostly to the west/north of the Great Lakes through Sunday... and short wave trough digging into the Pacific Northwest will cross the upper Midwest Monday and clip the upper Lakes with some height falls. Meanwhile high pressure builds east into the Great Lakes in the wake a cold front crossing the state tonight. Another weakening cold front may slip into Michigan overnight Tuesday. Primary Forecast Concerns: Pretty minimal at this point. By Sunday morning cold front looks to be largely through northern Lower Michigan. The only issue will be lingering post-frontal low clouds primarily over northern Lower (especially southeast) and a bit of drizzle. That could make for a bit of an interesting temperature forecast as persistent clouds may make for some cooler temperatures around HTL-Y31-OSC. On Monday a short wave trough just clips Upper Michigan but appears to have little impact on overall weather as looking at another dry day in a continued stretch of rain free weather. Warmer day expected on Monday with highs back in the 80s area wide. Weakening cold front settles in from the north Monday night...boundary itself may have little to work with but warm advection ahead of it may try to generate some rain showers south of M-72. .LONG TERM...(Monday night through Friday) Issued at 405 AM EDT Sat Aug 21 2021 High Impact Weather Potential: Minimal. Heading into the midweek period mean troughing will still be in place across western North America...leading to westerly or west- southwesterly flow aloft into the Great Lakes. This implies the potential for a west-east oriented frontal boundary for southern Wisconsin/southern Lower Michigan...and perhaps some short wave energy in the Thursday time frame. Tuesday looks to be another warm day provided cloud cover doesn't get in the way. Better chances for rain may finally be on the way heading into Wednesday. Possibly cooler but dry Thursday and seasonably cool Friday. && .AVIATION...(For the 12Z TAFS through 12Z Sunday morning) Issued at 647 AM EDT Sat Aug 21 2021 High pressure centered over northern Michigan will help keep VFR cigs/visibilities in place through the majority of the TAF period for all sites. Any residual patchy fog should burn off shortly after sunrise. A cold front approaching from the west will support scattered showers and perhaps a few storms across northwest portions of the area later this evening/tonight. Mainly south winds of 10 mph will switch to northerly winds after the frontal passage around midnight for all TAF sites excluding APN, which will be about two hours later. More widespread cloud cover will also accompany the arrival of the front, but sign are expected to remain above MVFR criteria. && .MARINE... Issued at 405 AM EDT Sat Aug 21 2021 The pressure gradient across the Great Lakes will begin to tighten today as a cold front approaches from the west. Southerly/south- southwesterly winds will increase throughout the morning, especially over Lake Michigan. Advisory-level winds are expected over the Lake Michigan nearshore waters and Whitefish Bay beginning later this morning and lasting into this evening. Winds will switch to northerly behind the frontal passage tonight. && .APX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LH...NONE. LM...SMALL CRAFT ADVISORY until 8 PM EDT this evening for LMZ344>346. LS...SMALL CRAFT ADVISORY from 2 PM this afternoon to 8 PM EDT this evening for LSZ321. && $$ UPDATE...JZ NEAR TERM...DJC SHORT TERM...JPB LONG TERM...JPB AVIATION...DJC MARINE...DJC